Egypt is investigating jailed ex-president Mohamed Mursi in connection with documents that judicial investigators say were leaked to the Qatar-based Al Jazeera satellite news channel, security sources said on Thursday.

Relations between Qatar, a Gulf Arab state, and Egypt have been tense since mid-2013 when then-army chief Abdel Fattah al-Sisi toppled the Islamist Mursi after mass protests against his rule. Qatar supported Mursi and his Muslim Brotherhood.